文章信息/Info

Title:

Aging phenomenon in ferroelectrics and the related large recoverable electro-strain effect

作者:

張立學;  任曉兵

西安交通大學，材料科學與工程學院，金屬材料強度國家重點實驗室，前沿科學技術研究院

Author(s):

ZHANG Lixue;  REN Xiaobing

State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, and Frontier institute for Science and Technology, Xi’an Jiaotong University

關鍵詞:

鐵電時效; 鈦酸鋇體系; 點缺陷; 對稱性原理; 電致應變

DOI:

10.7502/j.issn.1674-3962.2016.06.07

文獻標志碼:

A

摘要:

鐵電材料的性能在鐵電相變后會產生隨時間變化的“時效現(xiàn)象”。鐵電時效現(xiàn)象對鐵電材料的應用產生重要影響，導致其性能可靠性下降。鐵電時效與可動點缺陷（如氧空位）的擴散密切相關，但其微觀機理一直未被闡釋清楚。核心問題是無法理解鐵電相變?yōu)槭裁磿�驅動點缺陷擴散。作者基于其所提出的鐵電晶體中的點缺陷短程有序對稱性原理（X Ren, Nature Materials, 3: 91, 2004），指出：鐵電相變后，晶體對稱性發(fā)生改變，點缺陷短程有序對稱性受控于晶體對稱性而發(fā)生改變的這一原理驅動了點缺陷的擴散。進一步，通過時效調控晶體點缺陷的對稱性，產生電場下可逆的電疇翻轉，在鈦酸鋇鐵電材料中發(fā)現(xiàn)了40倍于傳統(tǒng)電致應變的巨大可回復電致應變效應。該結果為開發(fā)大電致應變材料提供了途徑。此外，通過原位偏光顯微鏡觀察驗證了可逆疇翻轉過程，為可回復大電致應變提供了直接的介觀證據(jù)。并對電子順磁共振譜線進行分析，證明了點缺陷具有與晶體對稱性一致的軸向對稱性。同時指出，利用晶體對稱性與點缺陷對稱性發(fā)生改變時的時間差，可獲得多尺度的新奇效應。

Abstract:

Ferroelectric aging usually refers to a gradual changing of properties with time. It lowers the reliability of ferroelectric devices and is usually undesirable for ferroelectrics. The occurrence of aging is closely related with the diffusion of mobile defects in ferroelectrics, yet a microscopic mechanism remains unclear. In the present paper, the authors pointed out that aging is microscopically driven by a symmetry conforming force of defect symmetry to crystal symmetry, based on the proposed symmetry-conforming short-range-order (SC-SRO) principle of point defects in ferroelectric crystals (X Ren, Nature Materials, 3: 91, 2004). More importantly, a giant recoverable electro-strain in aged BaTiO3-based ferroelectrics was obtained via a defect mediated reversible domain switching, which is 40 times larger than the traditional electro-strain effect. The results provide a promising way for designating high electro-strain materials. Besides, direct evidence for the reversible domain switching process behind the large recoverable electro-strain was given by an in situ polarizing microscope observation. The symmetry relation between point defects and crystals was also discussed in light of the SC-SRO principle and electron paramagnetic resonance spectroscopy. Multi-scale novel effects are expected from the time-lag between the symmetry changing of crystals and point defects.